This application is based on and incorporates herein by reference Japanese Patent Application No. 11-362180 filed on Dec. 21, 1999.
The present invention relates to a method and apparatus for processing an output of a position measurement sensor having non-contact type measurement elements for measuring a position of a movable body. For instance, such a method can be used for failure determination of a throttle valve position sensor having non-contact type measurement elements (e.g., Hall elements, a Hall ICs or the like) for measuring a rotational angle of a throttle valve that adjusts the amount of intake air supplied to an internal combustion engine.
There is one type of known throttle valve position sensor that has a couple of Hall ICs to provide double outputs, implementing a redundant system and allowing detection of a failure mode of the Hall ICs.
In such a throttle valve position sensor, a difference between an output of one Hall IC and an output of another Hall IC is continuously compared with a reference value to detect a failure mode. For instance, once a position of the throttle valve is incremented to fall within a high throttle valve position zone, an output of at least one Hall IC is raised and is fixed at 5 (V) that is equal to a power supply voltage applied to the sensor. Even if this Hall IC is normal, it is impossible to determine whether there is any abnormality (e.g., short circuit) in the Hall IC based on the output of the Hall IC. As a result, a detectable range of the failure mode of the throttle valve position sensor is disadvantageously limited to a lower throttle valve position zone within an operating range of the throttle valve position.
The present invention addresses the described disadvantage. Therefore, it is an objective of the present invention to provide a method and apparatus for processing an output of a redundant position measurement sensor having a couple of non-contact type measurement elements for measuring a position of a movable body, the method allowing detection of all failure modes of the sensor throughout an entire operating range of the movable body.
To achieve the objective of the present invention, there are provided a method and apparatus for processing an output of a redundant position measurement sensor having a couple of non-contact type measurement elements for measuring a position of a movable body. Maximum and minimum output voltages of the measurement elements are set to exceed upper and lower tolerance limits for output voltages of the measurement elements at upper and lower borders of an operating range of the measurement elements, respectively. Furthermore, the maximum and minimum output voltages of the measurement elements are also set to fall between upper and lower failure reference voltage ranges. The upper and lower failure reference voltage ranges are set by an electronic control unit connected to the measurement elements and are provided at upper and lower borders of a power supply voltage applied to the measurement elements, respectively.